Some biological molecules are sufficiently stable that they can be isolated, purified and then stored in solution at room temperature. However, this is not possible for many materials and techniques involving storage at low temperature, addition of stabilisers, freeze-drying, vacuum formation and air-drying have been tried to ensure shelf preservation. Despite the availability of these techniques, some biological materials still show unsatisfactory levels of stability during storage and some techniques lead to added cost and inconvenience. For example, refrigerated transportation and storage is expensive. Further, refrigerated transport is often not available for the transport of medicines such as vaccines in countries in the developing world.
In particular, the stresses of freeze-drying or lyophilisation can be very damaging to some biological materials. Freeze drying of biopharmaceuticals involves freezing solutions or suspensions of thermosensitive biomaterials, followed by primary and secondary drying. The technique is based on sublimation of water at subzero temperature under vacuum without the solution melting. Freeze-drying represents a key step for manufacturing solid protein and vaccine pharmaceuticals. The rate of water vapour diffusion from the frozen biomaterial is very low and therefore the process is time-consuming. Additionally, both the freezing and drying stages introduce stresses that are capable of unfolding or denaturing proteins.
Proteins are molecules with defined primary, secondary, tertiary and in some instances quaternary structures. The structure plays an important role in giving a protein its specific biological function. Unfortunately, the structural complexity of biological pharmaceuticals such as proteins makes them susceptible to various processes that result in structural and functional instability. Conformational integrity and functional groups must be protected from degradation
Instability can be a consequence of a variety of covalent and non-covalent reactions or modifications in solution. Degradation is generally classified into two main categories: firstly physical degradation or non-covalent pathway degradation and secondly the covalent degradation pathway.
Proteins can degrade via physical processes such as interfacial adsorption and aggregation which can significantly reduce a protein drug's potency and stability. A second consequence is that unfolding mediated by adsorption at an interface can often be an initiating step for irreversible aggregation of the protein in solution. Exposure of the protein's core at a hydrophobic surface can result in adsorption as a consequence of agitation, temperature or pH induced stresses; all of which can lead to aggregation.
Proteins may be subject to chemical modification such as oxidation, isomerisation, hydrolysis, disulfide scrambling, beta elimination, deamidation, and adduct formation. The principal hydrolytic mechanisms of degradation include peptide bond hydrolysis, deamidation of asparagine and glutamine and the isomerisation of aspartic acid. A common feature of the hydrolytic degradation pathway is that one significant formulation variable, with respect of the rates of the reactions is the pH.
As protein stability can significantly affect the safety and efficacy of a therapeutic, the composition of components in a biopharmaceutical formulation can affect the extent of protein degradation. The method of formulation of a biopharmaceutical also can impact the ease and frequency of administration.
Due to problems with instability and aggregation, most current stable formulations of proteins are not liquid formulations. Typically proteins are freeze dried (lyophilised) to provide stable formulations of the proteins. A bulking agent is often present in the formulations. The freeze dried formulations are distributed and stored in dried form, typically as a powder, in a sealed vial, ampoule or syringe. For example, WO 97/04801 describes stable lyophilised formulations of anti-IgE antibodies which have to be reconstituted immediately prior to use.
WO-A-2006/0850082 reports a desiccated or preserved product comprising a sugar, a charged material such as a histone protein and a dessication- or thermo-sensitive biological component. The sugar forms an amorphous solid matrix. However, the histone may have immunological consequences if the preserved biological component is administered to a human or animal.
WO 2008/114021 describes a method for preserving viral particles. The method comprises drying an aqueous solution of one or more sugars, a polyethyleneimine and the viral particles to form an amorphous solid matrix comprising the viral particles. The aqueous solution contains the polyethyleneimine at a concentration of 15 μM or less based on the number-average molar mass (Mn) of the polyethyleneimine and the sugar concentration or, if more than one sugar is present, total sugar concentration is greater than 0.1M.
WO 2010/035001 describes a method for preserving a polypeptide in which an aqueous solution of the polypeptide is dried, for example freeze dried, in the presence of one or more sugars and a polyethyleneimine (PEI). The resulting dried composition is typically provided as a stable dry powder in a sealed vial, ampoule or syringe. A solution is reconstituted from the powder in order to administer the polypeptide to a patient e.g. by injection.
Drying and especially freeze drying are however costly and time-consuming processes. It would be advantageous if their use could be avoided. Biologically active materials often suffer a loss of activity following heating and drying. Additionally, the need to reconstitute a freeze dried powder in a solvent before use of the polypeptide is an inconvenience. Indeed, it can carry risks for the patient or medical professional who performs the reconstitution step if the procedure is not carried out correctly.
It is thus advantageous to provide liquid virus and protein formulations that do not require reconstitution in order to be used. Consequently, there is a demand for stable liquid injectable virus and protein formulations. There is a demand for highly concentrated stable liquid injectable antibody formulations.